Vilazodone is 5-(4-[4-(5-cyano-1H-indol-3-yl)butyl]piperazin-1-yl) benzofuran-2-carboxamide and represented by formula (I).

The product is marketed in the form of Hydrochloride salt. The current pharmaceutical product containing this drug is being sold by Merck using the trade name Viibryd. Vilazodone is an SSRI antidepressant developed by Clinical Data for the treatment of major depressive disorder.
Vilazodone was first described in U.S. Pat. No. 5,532,241. Example 4 of Said patent described process for preparing vilazodone by reacting 1-[4-{5-cyanoindol-3-yl)butyl]-4-{2-carboxybenzofuran-5-yl)-piperazine at first with 2-chloro-1-methylpyridinium methanesulfonate in N-methylpyrrolidine and then with dried ammonia. Customary working up gives the free base vilazodone. Which is further converted in to Vilazodone hydrochloride.
Journal of Medicinal Chemistry (2004), 47(19), 4684-4692 disclose process for preparation of vilazodone as per below scheme.

Org. Process Res. Dev., 2012, 16 (9), pp 1552-1557 discloses process as per below scheme.

The main problem associated with these processes is that it involves use of less economical reagent such as 2-chloro-1-methylpyridinium methane sulphonate and solvent such as N-methyl pyrrolidine.
Zhongguo Yaowu Huaxue Zazhi (2012), 22(1), 74-75, 81 discloses many possible ways for synthesis of vilazodone.
None of the prior art disclosing direct conversion of ester to amide. All prior art references shows first conversion of ester of compound of formula II in to corresponding acid and then reaction of acid with ammonia in presence of solvent and catalyst to prepare vilazodone.
Org. Process Res. Dev., 2012, 16 (9), pp 1552-1557 article disclose that no vilazodone was obtained during direct conversion of ester to amide.
The above processes for preparation of Vilazodone require many numbers of steps and involve unfriendly reagents. The process is less economical, relatively less safe and time-consuming. Hence such technology is not readily suitable for commercial production. Therefore, the present invention provides a process in which directly ester converts in to amide.
PCT Publication No. WO2002102794A2 describes different polymorphs of Vilazodone hydrochloride, termed as form I to form XVI. WO2002102794A2 describes form XVI as amorphous form. The term “amorphous” means a solid without long-range crystalline order. However, the X-ray powder diffraction pattern of form XVI shows that the polymorph is not in its pure amorphous form but also comprises crystalline peaks. Therefore, it does not demonstrate the amorphous nature of the product. It is essentially a mixture of crystalline and amorphous form which is not a form of suitable choice.
Polymorphic purity is one of the important aspects in the development of any active pharmaceutical ingredients. An active pharmaceutical ingredient is always preferred to have consistency in terms of polymorphic purity. Therefore it is desirable to have either pure crystalline form or a substantially pure amorphous form.
Solvent medium and mode of isolation play very important role in obtaining a polymorphic form over the other.
Accordingly, there remains a need in the art for a novel, stable and substantially pure amorphous form of Vilazodone hydrochloride. The present inventors have directed its research work to get the desired polymorphic purity.
Based on the aforementioned drawbacks, prior art processes found to be unsuitable for preparation of vilazodone at lab scale and commercial scale operations.
Hence, a need still remains for an improved and commercially viable process of preparing pure vilazodone or a pharmaceutically acceptable salt thereof that will solve the aforesaid problems associated with process described in the prior art and will be suitable for large-scale preparation, in lesser reaction time, in terms of simplicity, purity and yield of the product.